Photometric study of new southern SU UMa-type dwarf novae and candidates: V877 Ara, KK Tel and PU CMa     

Taichi Kato  Roland Santallo  Greg Bolt  Tom Richards  Peter Nelson  Berto Monard  Makoto Uemura  Seiichiro Kiyota  Rod Stubbings  rew Pearce  Tsutomu Watanabe  Patrick Schmeer  Hitoshi Yamaoka 《Monthly notices of the Royal Astronomical Society》2003,339(3):861-871

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Acoustic evidence for unusual diel behaviour of a mesopelagic fish (Vinciguerria nimbaria) exploited by tuna   总被引：1，自引：0，他引：1  

Marchal  Emile; Lebourges  Anne 《ICES Journal of Marine Science》1996,53(2):443-447

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Is the spring water responsible for the fossilization of faunal remains at Florisbad, South Africa?     

Rod M. Douglas 《Quaternary Research》2006,65(1):87-95

It is has been suggested that faunal remains at Florisbad were fossilized in a spring context due to the mineralized spring water. However, the environment conducive to the precipitation of CaCO₃ and other authigenic minerals was formed largely through the salinization of the organic layers and clay, and the mineralization of the groundwater. Factors contributing to this favorable environment include: CaCO₃ saturation, pH, the decomposition of halophytes, Eh, rainfall, biomineralization, and aeolian deposition. With the exception of pH, none of the above factors feature in a spring context, with evidence suggesting that the spring water may historically never have carried sufficient minerals for fossilization, and that contact with the spring water may actually have resulted in the demineralization of previously fossilized material. In light of this evidence, it is concluded that the fossilization of faunal remains at Florisbad took place in a sedimentary organic matter and clay environment and could not have taken place in the spring vents where there is an undersaturation of Ca.  相似文献   

A Theoretical Comparison of Tsunamis from Dislocations and Landslides   总被引：1，自引：0，他引：1  

Emile A. Okal  Costas E. Synolakis 《Pure and Applied Geophysics》2003,160(10-11):2177-2188

— We use simple physical models to evaluate and compare the orders of magnitude of the energy generated into a tsunami wave by seismic dislocations and underwater slumps. We conclude that the two sources can generate tsunamis of comparable total energy. However, the slumping source is shown to be fundamentally dipolar in nature, which results in a low-frequency deficiency in the far-field. These simple conclusions corroborate the interpretation of the 1998 Papua New Guinea tsunami as being generated by an underwater slump.  相似文献   

The earthquake and tsunami of 1865 November 17: evidence for far-field tsunami hazard from Tonga   总被引：1，自引：0，他引：1  

Emile A. Okal  José Borrero  Costas E. Synolakis 《Geophysical Journal International》2004,157(1):164-174

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Hydro-geochemistry of groundwater and surface water in Dschang town(West Cameroon): Alkali and alkaline-earth elements ascertain lithological and anthropogenic constraints          下载免费PDF全文

Yemeli Elida Joelle  Temgoua Emile  Kengni Lucas  Ambrosi Jean-Paul  Momo-nouazi Mathieu  Silatsa-Tedou Francis Brice  Wamba Franck Robean  Tchakam-Kamtchueng Brice 《地下水科学与工程》2021,9(3):212-224

This study focuses on the sources of alkali and alkaline-earth elements based on the geochemistry of groundwater and surface water in Dschang concerning environmental and anthropogenic constraints. A comprehensive set of 50 samples from groundwater and surface water were analyzed by ICPMS and processed by spatial interpolation in a GIS environment. The results highlight a geochemical anomaly at the center of the densely inhabited area subject to a profusion of open dumps discharges. This anomaly with the highest spatial contents of Be(Cs, Rb, Mg) suggests an anthropogenic source that demarcates with the lowest alkali and alkaline-earth elements on the peripheral area of Dschang. Other findings include lithological constraints with volcanic rocks being the main source compared to granitoid.The study points out good correlations between Be, Cs, Rb and Mg spatial distributions and physicochemical parameters of waters(K, EC, TDS), and inversely with the lowest p H. p H is established as the most functioning physico-chemical constraint of alkali and alkaline-earth mobility in Dschang. The p H lowest values within the geochemical anomaly also highlight the impact of human activities on water acidity, which later enhance elements mobility and enrichment. Despite low elements contents relative to WHO standards, our findings point out an example of anthropogenic impact on water geochemistry linked to solid waste pollution; it also demonstrates significant anthropogenic changes of environmental physicochemical parameters of prime importance in the mobility and distribution of elements in the study area.Similar assessments should be extended in major towns in Cameroon.  相似文献   

Seismic parameters controlling far-field tsunami amplitudes: A review   总被引：3，自引：1，他引：3  

Emile A. Okal 《Natural Hazards》1988,1(1):67-96

We present a review of the influence of various parameters of the sources of major oceanic earthquakes on the amplitude of tsunamis at transoceanic distances. We base our computations on the normal mode formalism, applied to realistic Earth models, but interpret our principal results in the simpler framework of Haskell theory in the case of a water layer over a Poisson half-space. Our results show that source depth and focal geometry play only a limited role in controlling the amplitude of the tsunami; their combined influence reaches at most 1 order of magnitude down to a depth of 150 km into the hard rock. More important are the effects of directivity due to rupture propagation along the fault, which for large earthquakes can result in a ten-fold decrease in tsunami amplitude by destructive interference, and the possibility of enhanced tsunami excitation in material with weaker elastic properties, such as sedimentary layers. Modelling of the so-called tsunami earthquakes suggests that an event for which 10% of the moment release takes place in sediments generates a tsunami 10 times larger than its seismic moment would suggest. We also investigate the properties of non-double couple sources and find that their relative excitation of tsunamis and Rayleigh waves is in general comparable to that of regular seismic sources. In particular, landslides involving weak sediments could result in very large tsunamis. Finally, we emphasize that the final amplitude at a receiving shore can be strongly affected by focusing and defocusing effects, due to variations in bathymetry along the path of the tsunami.  相似文献   

Amino acid nitrogen in atmospheric aerosols: Occurrence,sources and photochemical modification   总被引：2，自引：0，他引：2  

Peter J. Milne  Rod G. Zika 《Journal of Atmospheric Chemistry》1993,16(4):361-398

The presence of amino acids in atmospheric precipitation and aerosols has been noted for many years, yet relatively little is known about these or other nitrogen containing organic compounds in the atmosphere. Marine and continental rainwater analyses indicate that atmospheric aerosols, and subsequently atmospheric precipitation, may contain substantial levels of free and combined amino acids. The most likely source of amino N in the remote marine atmosphere appears to be the injection of proteinaceous material through the action of bursting bubbles at the sea-air interface or the long range transport from terrestrial sources. The capacity of these substrates to undergo photooxidation and photodegradation in the atmosphere to simpler species, such as ammonium ions, carboxylic acids, and for the S containing amino acids, oxidized forms of sulfur, has received little attention from atmospheric chemists. The photochemistry of covalently bound amino groups, particularly as found in peptides and amino acids, is discussed here with the purpose of summarizing what is known of their occurrence and their possible importance to atmospheric chemistry.  相似文献   

Geography in Australian education     

Rod Gerber 《GeoJournal》1990,20(1):15-23

Geography in Australia has a heritage that is strongly British, but more recently has been influenced from other parts of the world, such as North America and New Zealand. Its popularity has fluctuated and it is now under threat as a separate subject in the compulsory years of schooling. In higher education, geography has retrieved lost ground to be a popular area of study, but not a research area in the current national priorities. Geography plays a focal role in the general education of Australians. It is a medium for education involving the education of people, about, in, and for the society and environment in which they live. Through education, geography will enable people to explore their life-roles as learners, social beings, recreators, producers, consumers and citizens. It will develop in people distinctive knowledge, thinking processes, attitudes and values, and encourage participation in social and environmental actions. Teachers in secondary and higher education have differing and distinctive roles. Being a geographer in Australia does have benefits including: working in an identifiable area of knowledge maintaining a bridge across the physical and social sciences; the promotion of inquiry approaches and as a focus for the various adjectival educations that have emerged. These are tempered by challenges such as: threats from emerging disciplines, current national research priorities and the movement to social science education. Therefore, promotion of geography in Australia needs to be much more forceful than it has until now. The work of groups such as the Institute of Australian Geographers and the Australian Geography Teachers' Association needs to be co-ordinated more closely to develop a strong lobby for geography in Australian education.  相似文献   

Far-field simulation of the 1946 Aleutian tsunami   总被引：1，自引：0，他引：1  

Emile A. Okal  Hélène Hébert 《Geophysical Journal International》2007,169(3):1229-1238

We present hydrodynamic far-field simulations of the Aleutian tsunami of 1946 April 1, using both a dislocation source representing a slow earthquake and a dipolar one modelling a large landslide. The earthquake source is derived from the recent seismological study by López and Okal, while the landslide source was previously used to explain the exceptional run-up at Scotch Cap in the near field. The simulations are compared to a field data set previously compiled from testimonies of elderly witnesses at 27 far-field locations principally in the Austral and Marquesas Islands, with additional sites at Pitcairn, Easter and Juan Fernández. We find that the data set is modelled satisfactorily by the dislocation source, while the landslide fails to match the measured amplitudes, and to give a proper rendition of the physical interaction of the wavefield with the shore, in particular at Nuku Hiva, Marquesas. The emerging picture is that the event involved both a very slow earthquake, responsible for the far-field tsunami, and a major landslide explaining the near-field run-up, but with a negligible contribution in the far field.  相似文献